From continuous vibration monitoring to FEM-based damage assessment: Application on a stone-masonry tower

The paper presents a damage assessment strategy suitable to historic masonry towers. The methodology is exemplified using the data collected in the continuous dynamic monitoring of the San Vittore bell-tower (Arcisate, Northern Italy). The proposed damage assessment procedure aims not only at detecting the occurrence of structural anomalies, but also at localising the damage in the investigated structure. After a brief description of the tower and past diagnostic survey (including ambient vibration tests and Finite Element modelling), the results of the continuous dynamic monitoring are highlighted and the effect of temperature on automatically identified resonant frequencies is discussed. Subsequently, regression models based on Principal Component Analysis are applied in order to filter out the fluctuations caused by the environmental effects on the identified resonant frequencies. The damage detection and damage localisation issues are then addressed by using novelty analysis tools. The effectiveness of the proposed strategy is demonstrated through the detection and localisation of realistic damage scenarios simulated with the baseline Finite Element model. Specifically, the damage localisation has been tackled by using the “cleaned” modal properties within a continuous Finite Element model updating scheme.